Jackson, Jeremy B.C.

English

Aquatic Commons

 ECOSYSTEM EXTINCTION AND THE FUTURE OF THE OCEANS 
 
JEREMY B. C. JACKSON 
Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0244, U. S. A. 
 
Ocean ecosystems are severely degraded by human impacts and entire marine ecosystems are increasingly threatened 
with extinction or degradation almost beyond recognition. The causes are numerous and complex, but can all be related to 
human resource extraction and pollution in the broadest sense. In the face of imminent and potentially irreversible loss, we 
need to open our eyes to how much and why the oceans have changed and to identify and act upon our realistic options for 
the future.  
 
How much and why have the oceans become degraded? 
The symptoms and causes of ocean degradation are so obvious that it is remarkable how reluctant we are to acknowl-
edge them. Six major changes are of particular concern: 
 
1. Overfishing: Most of the large animals are gone, including whales, sea turtles, sharks, and fishes of all kinds, and the 
reasons are obviously that we hunted them to oblivion. Fisheries biologists and managers argue whether or not the losses of 
big fishes like tunas or billfish are 70% or 90%, or whether we are “fishing down” or “fishing through” marine food webs, 
but the overwhelming evidence of loss is the serial economic collapse and closure of one fishery after another. There could 
be no clearer manifestation of “fishing down the food web” than the fact that the most valuable fisheries off eastern Canada, 
New England, and California today are invertebrates instead of fish, and similar trends are evident around the world. 
 
2. Trawling: The three-dimensional structure of most of the sea floor of coastal seas and continental shelves, and much 
of the deeper ocean, has been flattened by trawling to the point that the once complex communities of sponges, corals, bryo-
zoans and seaweeds have been transformed into vast sediment plains. The resulting loss of habitat, fin fisheries, and biodi-
versity requires decades to centuries to recover. 
 
3. Introduced species: Seaweeds like the “killer algae” Caulerpa are smothering entire bottom communities including 
the hard grounds and seagrass beds of the northwest Mediterranean and coral reefs of Hawaii, introduced shellfish popula-
tions have exploded in coastal seas, and introduced jellyfish clog fishing nets in the Gulf of Mexico. Most introductions are 
irreversible and the economic costs are enormous. 
 
4. Warming: The rise of carbon dioxide in the atmosphere due to the burning of fossil fuels is measurably warming the 
oceans, eliminating entire polar ecosystems, causing rapid poleward shifts in species’ distributions, and killing corals due to 
the breakdown in the coral-dinoflagellate symbiosis referred to as “coral bleaching.” A single bleaching event in 1998 in the 
Indian Ocean killed 20% of all the corals there, and episodes like this are of increasingly frequent and severe occurrence. 
Even more ominous are the expected effects of ocean acidification. Careful measurements have already demonstrated a 
drop of 0.1 pH units in the oceans, and experiments overwhelmingly demonstrate that calcareous organisms ranging from 
coccolithophores to reef corals cannot calcify or grow under even mildly acidic conditions. Moreover, increased stratifica-
tion of the oceans due to surface warming is apparently decreasing upwelling of nutrient rich waters with obvious implica-
tions for total productivity. Climate models suggest that the oceans may move into a permanent El Niño condition.  
 
5. Toxic Chemicals: Nearly half a century after Rachel Carson warned us of the effects of toxic chemicals in the envi-
ronment, the oceans are increasingly polluted by mercury from the burning of coal, PCBs, insecticides, and the entire pano-
ply of industrial chemicals that are allowed to run into the ocean sewer. These chemicals have built up to fatal concentra-
tions in many marine mammals, fish, and invertebrates and are a serious health hazard to people, especially in the Arctic, 
where substances produced by coal-fired power plants are shunted in the upper atmosphere to enter the marine food chains. 
 
6. Eutrophication: Nutrients and primary production are increasing throughout coastal seas due to the breakdown in the 
filtration capacity of organisms ranging from marsh plants to suspension feeders coupled with the massive introduction of 
nitrogen, phosphorous, and organic carbon due to inefficient land use and industrial agriculture and animal production. The 
result is runaway eutrophication I call “the rise of slime” and proliferation of coastal anoxic “dead zones” around the world. 
Breakdown of formerly complex food webs topped by abundant sharks, fish, sea turtles, and mammals results in greatly 
simplified, microbially dominated ecosystems with boom and bust cycles of toxic dinoflagellate blooms, jellyfish, and dis-
ease.  
 
The overall sequence of events in the degradation of coastal ecosystems is strikingly similar for seagrass, oyster reef, 
coral reef, kelp forest, or level bottom communities. First, the large animals are eliminated by hunting and fishing. Second, 
Page v  59th Gulf and Caribbean Fisheries Institute  
 
the three-dimensional structure built by large sessile organisms such as kelps and corals is lost either directly by trawling or 
indirectly due to disease, smothering by sediments, or climate change. Third, eutrophication is amplified by positive feed-
backs such that consumption cannot keep up with production. Microbial metabolism of unconsumed phytoplankton causes 
anoxia, mass mortality of animals, and a drop in the useful productivity of the entire ecosystem. Transitions in ecosystem 
state build in intensity through the additive and synergistic effects among ecosystems. Cessation of fishing or pollution does 
not always result in renewal of fish stocks and water quality, raising questions about the potential for ecosystem recovery. A 
big unknown is the extent to which eutrophication and its consequences may extend to the pelagic realm. 
 
What are the options for the future? 
“Business as usual” will have catastrophic consequences. Wild fisheries will be eliminated and coastal seas will be too 
toxic for aquaculture. Dead zones will extend to ring the continents and move increasingly seaward. Toxic blooms will be-
come chronic with increasingly severe consequences for human health and the seacoasts will become a global slum. Halting 
and possibly reversing this inexorable decline will require fundamental changes in fishing, agriculture, and energy produc-
tion that are still widely perceived as unrealistic and naïve. But as the consequences of “business as usual” become more 
and more apparent, such changes are inevitable, barring some magical technological solution. Three main actions are re-
quired: 
 
1. Stop most fishing and develop responsible aquaculture on a massive scale: 
In the face of 6.5 billion people, increasing global equity, and continued human population increase, sustainable wild 
fisheries are an oxymoron except for weedy species like sardines and anchovies and increasingly expensive luxury fish in 
the developed world. Aquaculture is the only logical alternative and we should promote industries that focus on species low 
on the food chain and how to raise them with minimal harmful ecosystem consequences. Besides their obvious value for 
stabilizing the world supply of fish and shellfish, scaling back increasingly competitive and technologically intensive fish-
ing would also contribute a modest reduction in energy consumption. 
 
2. “Green” the “Green revolution” by eliminating subsidies for fertilizers and pesticides and taxing wastes: Dead zones 
like the Chesapeake Bay and the Gulf of Mexico could be dramatically improved by removal of subsidies for and taxation 
of the gross overuse of fertilizers and pesticides for agriculture, lawns, and golf courses and the unregulated production and 
dumping of animal wastes. Reduced fertilizer and pesticide production would also significantly reduce energy consumption. 
The rise of slime is a major threat to the development of aquaculture and human health in the coastal zone because of in-
creasing frequency and severity of toxic blooms and disease. The challenges of such massive changes in agricultural prac-
tice are daunting, but readily and quickly achievable in developed countries that routinely destroy excess food they cannot 
sell or give away.  
 
3. Cap carbon emissions in 10 years and achieve large reductions by 2025: Increased ocean warming, stratification, and 
acidification have been documented for more than twenty years, and the rates of change are increasingly nonlinear. The link 
to burning of fossil fuels is established and the adverse biological consequences are clearly demonstrated by field observa-
tions and experiments. Failure to cap and reduce emissions now will almost certainly result in the loss of coral reefs and 
most other calcifying organisms, including major groups of primary producers and seafood species. 
 
Coda 
The record of actions to preserve our oceans is dismal in the extreme. The laws of open access and the “tragedy of the 
commons” are commonly invoked as excuses for inaction, but great progress could be made to rationalize seafood produc-
tion and halt eutrophication on a case by case basis by nations and communities acting alone within their 200-mile exclusive 
economic zones. This is especially true for the wealthy nations of North America, Europe, Australia, and Japan, for which 
the only constraint to responsible behavior is greed. In contrast, the causes and consequences of global change are obviously 
global, although the impact of the developed nations greatly exceeds that of the rest, and unilateral actions would have im-
mediate environmental benefits. The choice is all of ours to make. 
 


Ecosystem extinction and the future of the oceans

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Ecosystem extinction and the future of the oceans

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